The proposed research deals with the study of brain proteins that have important biological functions. Several years ago this laboratory discovered a high molecular weight protein in the adult brain which has the ability to stimulate the morphological and chemical differentiation of glioblasts in culture. Work is in progress for the purification and chemical characterization of this protein factor. We have detected two molecular forms for this protein factor: the high molecular weight form and its dissociation product the low molecular weight form. The "high form" is more stable than the "low form" although the latter is easier to be purified. We have obtained the low molecular weight form as a single band in the polyacrylamide gel and have prepared antibody against it. Characterization of the purified material and its antibody is currently under way.